There are a lot of factors that determine what the best choice of Balun is. Unless it is a resonant antenna, the impedance is not purely resistive, usually far from it. It can be almost anything. The feedline length will affect what the impedance is at the tuner. The tuner, if you have one, will select, or you will select the configuration and values of inductance and capacitance that provide the correct match. Those components, especially the inductors have losses and heat up. You don't generally know what those losses are and they vary from part to part.
The tuner It can often match with a 1:1, 4:1 and other baluns, as long as the impedance seen by the tuner is within it's range. The claims that a tuner can tune 10:1 or 3:1 are not that useful, except for a general comparison. They can't match every possible impedance, inductive, capacitive or whatever within that range. Depending on the manufacturer's choices of values, they may be able to match a higher SWR if it is very inductive, rather than capacitive, for example. The optimal match will also be determined by the losses. You may be able to get a match, but 50% of your power may be absorbed by the tuner, with smoke eventually being let out. I use a homebrewed dual core switchable 4:1 / 1:1 currrent balun. Most of the time, the tuner can match my Horizontal loop with the switch in either position. It may result in a lower SWR in one position or the other and I usually choose the position that results in the lowest SWR after the tuner matches. In a few cases, after transmitting for a while, the tuner will try to retune. I believe that is likely due to an inductor heating up in the tuner and changing value. That tells me the losses are likely high and I try the other switch position and see if it stays tuned. If you know what impedance your antenna system and feedline present to the tuner, you may be able to choose an optimal balun. In my case, with so many bands, there is no single best choice. I choose whatever works best on that particular frequency. 73, Mark W7MLG On Sat, Feb 24, 2018 at 8:30 PM, Bob McGraw K4TAX <rmcg...@blomand.net> wrote: > I question the 4:1 balun being the correct nor best choice. Typical of > that antenna the feed Z of the radiator is more likely 25 to 35 ohms. The > 4:1 balun is presenting something like 10 ohms to the tuner. Worst case for > high current and hi loss in the tuner causing heating. A 1:1 balun would > seem more likely correct. > > Many seem to "think" a 4:1 balun is correct when using open wire or a > balanced line to "match the line". > > Bob, K4TAX > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
